PREDICTION OF VOLUME FRACTION AND GRAIN-S IZE OF FERRITE UNDER INTERCRITICAL ROLLING OF LOW-CARBON STEELS

Static recovery and recrystallization behavior of alpha grains of low carbon steels have been studied by means of hot working simulator. Sta tic recovery rate increases as carbon content increases up to 0.02mass % and is nearly constant above 0.02mass%. The critical strain for recr ystallization, epsilon(m), decreases with decreasing initial grain siz e and strain rate and with increasing deformation temperature. Recryst allized grains are developed within an interval of 50 ms alter straini ng over epsilon(m). Recrystallized alpha grain sizes decrease with dec reasing initial grain size and deformation temperature, and with incre asing strain. Recrystallized fraction increases with decreasing initia l grain size and with increasing strain and deformation temperature. 2 -step hot working tests at various temperatures above and below Ae(3) have been carried out to examine the strain induced transformation fro m hot worked austenite to ferrite. On the basis of these results, a pr ediction model of alpha volume fraction and grain size is developed an d its availability in the case of intercritical rolling was certified.